This study examines the ability of monkeys to detect small temperature changes in the noxious range applied to the wrist. Once the animal is trained to detect samll temperatures, the response of somatosensory cortical neurons will be correlated with the monkey's ability to detect small increments in temperature in the noxious range. In addition, the monkey's ability to detect small thermal increments on the wrist are compared with previous results obtained from the face. These data provide a direct comparison between the relative sensitivities of the face and of the wrist of thermal stimulation in the noxious range.